Spark plug shield



Jan., 26, 1937. H, RABEZZANA 2,069,046

SPARK PLUG SHIELD Filed Jan. 12, 1935 Patented Jan. ze, 1937 SPARK PLUG SHIELD Hector Rabezzana, Flint,

Mich., assignor to General Motors Corporation, Detroit, Mich., corporationcof Delaware Application January 12, 1935, Serial No. 1,559

4 Claims. (Cl. 12S-169) My invention relates to spark plug shields designed to prevent high tension current supplied to a spark plug from interfering with radio sending and receiving sets located adjacent thereto, this being accomplished by enclosing the spark plug in a metallic casing structure which screws into an opening in an internal combustion engine head corresponding with the usual opening provided for the spark plug, and which shield is therefore grounded upon the engine with which the plug is used. The high tension cable whereby current is supplied to the plug is ordinarily provided with a metallic covering which is connected with the casing structure and grounded thereupon so that both the supplyv conductor and the plug itself :are shielded, and disturbance of adjacent radio apparatus by high voltage current in the secondary of the ignition system oi the engine is prevented.

The preferred form of my invention is illustrated in the accompanying drawing, and the particular features wherein the same consists are particularly pointed out in the claims at the end of this specication.

In the drawing:

Figure 1 is a view showing a spark plug shield made in accordance with my invention, in elevation, and screwed in place in an opening provided in a cylinder head.

Figure 2 is a view drawn to about twice the scale of Figure 1 and showing a central longitudinal section of my improved spark plug shield,

with a spark plug in place within the same.

Figure 3 is a View showing the base of the shield I and the lower end of the tubular upper part, thereof separated, and both in perspective.

Figure 4 is a view showing a section upon a transverse plane indicated by the line 4-4, Figure 2, looking down.

Referring now to the drawing, the numeral 5 designates part of kthe head of aninternal combustion engine cylinder, the same having a threaded opening which may be the opening provided for receivingthe larger standard size of spark plug; as the spark plug 6 with which the shield herein is desrihed for use is pf small size, such as is commohy designated as a 10 mm. (millimeter) plug, ythe threaded opening in the cylinder head being of a diameter adapted to receive a 14 mm./spark plug.

The-numeral 1 designates a base or adapter having a depending tubular part 8 which is externally threaded to screw into the opening aforesaid in the cylinder head, and is also threaded internally to receive the spark plug 6. The upper The numeral I2 designates a metallic tubular 5 casing enclosing the plug 6 as shown. 'I'his casing is permanently secured to the base 1 as by being welded or brazed thereto, the diameter of the casing preferably corresponding with that of the upper end of the base. As shown the lower 10 end of the casing is provided with lugs I3 bent inward at their ends and which lugs lie within the outer parts of the grooves whereby more area is provided for the welded or brazed joints between the parts, and a stronger connection be- 15 tween the two is secured. The inner parts of the .pairs of grooves 9 9 and IIl-Ill provide recesses inside the tubular casing I2, designated by the numeral I4 in Figure 2, to be engaged by a tubular Spanner wrench inserted through the open 20 upper end of the casing in screwingv the base 'I into the threaded opening in the cylinder head, or when the base and casing are to be removed from the head. The spark plug 6 is likewise put in place or removed for inspection or replacement by a socket wrench inserted through the upper end of the casing. The casing I2 is commonly lined with a tubular insulating material I5 which may be of mica, bakelite, or fabric material coated with an insulating varnish, or the inside of the casing may be provided with a coating of a suitable insulating enamel. The wall of the casing is formed with inwardly displaced rings at I6, I'l above and below the insulating' member I5 for holding it in place,. and whereby 35 circumferential grooves are provided in said casing.

The open upper end of the casing is closed by a removable and replaceable cover I8 which is slidable over the upper part thereof, and the wall 4 of which cover is slitted to provide a resilient catch I9 the free end of which enters the external groove provided by the upper ring I6 to thereby retain the cover in place upon the casing I2. This cover is open at its upper end; and a gland shown as made up of an exteriorly threaded part 2,0 soldered in place in said opening, and an internally threaded nut 2| engaging said threaded part, provides a passage through which a current supply conductor 22 enters the casing I2 and connects with the central electrode of the plug 6 through a suitable terminal 23. The supply conductor` 22 is commonly provided with a metallic sheath 24, usually in the form of a braided covering or a flexible tube; and this sheath ls connected with the gland in any suitable way as by providing a ange at its end, which flange is grasped between the gland members 20, 2l, as shown in Figure 2, whereby the sheath 24 is electrically connected with the metallic cover I8. The cover being in contact with the metallic casing I2, and the latter being grounded to the engine cylinder through the base 7, it therefore follows that both the supply conductor 22 and the spark plug 6 are shielded, thereby preventing high tension currents supplied to the spark plug from interfering with the proper operation of adjacent radio apparatus.

Having thus described and explained my invention I claim and desire to secure by Letters Patent:

l. In a spark plug shielding device, a base having a shield supporting part at its upper end, and a depending tubular part which is threaded externally to screw into a threaded opening, and threaded internally to receive a spark plug; a tubular casing secured to said base and supported thereby and extending upwardly therefrom, so as to enclose a spark plug supported by said base; a lining of insulating material within said casing; a slidable cover fitting outside the upper part of said casing for closing the open end thereof; and a gland carried by the upper end of said cover and through which a supply conductor may enter into said casing, and whereby a sheath surrounding said supply conductor may be secured to the upper end of said cover.

2. In a spark plug shielding device, a base having oppositely located radial grooves at its upper end, and a depending tubular part which is threaded externally tcI screw into a threaded opening, and threaded internally to receive a spark plug; a tubular casing corresponding in diameter with the upper end of said base and which casing is permanently secured to said upper end, and has lugs which extend into and lie within the outer parts of said grooves whereby said grooves provide Spanner wrench receiving recesses disposed inside and adjacent the lower end of said tubular casing; a lining of insulating material within said casing; a cover for closing the upper end of said casing; and a gland carried by the upper end of said cover and through which a supply conductor may enter into said casing, and whereby a sheath surrounding said supply conductor may be secured to the upper end of said cover.

3. In a spark plug shielding device, a base having oppositely located radial grooves at its upper end, a spark plug seat dsposedbelow said grooves, and a depending tubular part which is threaded externally to screw into a threaded opening, and threaded internally to receive a spark plug; a tubular casing corresponding in diameter with the upper end of said base and which casing is permanently secured to said upper end, and has lugs which extend into and lie within the outer parts of said grooves whereby said grooves provide Spanner wrench receiving recesses disposed inside and adjacent the lower end of said tubular casing; a lining of insulating material within said casing; a cover for closing the upper end of said casing; and a gland carried by the upper end of said cover and through which a supply conductor may enter into said casing, and whereby a sheath surrounding said supply conductor may be secured to the upper end of said cover.

4. In a spark plug shielding device, a base having a shield supporting part at its upper end, and a depending tubular part which is threaded externally to screw into a threaded opening, and threaded internally to receive a spark plug; a tubular casing secured to said base and supported thereby and extending upwardly therefrom, so as to enclose a spark plug supported by said base; a lining of insulating material within said casing; a slidable cover fitting outside the upper part of said casing for closing the open end thereof, and which cover has a resilient catch cut free from its wall and the free end of which catch is adapted to engage within a groove formed in the wall of said tubular casing; and a gland carried by the upper end of said cover and through which a supply conductor may enter into said casing, and whereby a sheath surrounding said supply conductor may be secured to the upper end of said cover.

HECTOR RABEZZANA. 

